1. Field of the Invention
The present invention relates to a sheet gripper for gripping printing material sheets, in which a dimensionally stable base material and an elastic clamping surface material, which forms a clamping surface, are joined to each other.
Such a sheet gripper is described in published, non-prosecuted German patent application DE 31 46 836 A1. In the case of this sheet gripper from the prior art, over the course of time the clamping surface material can separate from the base material. The separated base material can wander about in the machine and cause consequential damage. For example, it can adhere to a printing material sheet and, together with the latter, run into a press nip and increase the printing pressure therein excessively, so that cylinders forming the press nip or their mountings are damaged.
German patent DE 37 39 169 C1, corresponding to U.S. Pat. No. 4,970,955, is not able to make any truly helpful contribution to solving the problem thrown up. According to the last-named prior art, the sheet grippers cooperate with a gripper pad, whose clamping surfaces are formed from an elastic plastic. By contrast, the clamping surfaces of the sheet grippers are coated with a hard material.